At least 12 people suffered burns after a "strong acidic substance" was reportedly thrown in a bar in east London.
The revelers were partying at Wringer & Mangle, Sidworth Street, when an "unknown corrosive substance" believed to be acid was thrown early this morning.
The incident in London Fields, east London, forced the evacuation of the venue where around 600 clubbers had been at an event.
A hazardous response team along with other emergency services were called to the scene in the early hours of Monday morning.
One witness said that the suspected acid appeared to have been thrown over the face and arm...
Around 200 people had left the premises before the arrival of emergency services, while the building was evacuated of a further 400.
A neighbour who lives nearby told the BBC: "It happened so fast - they rushed people out". A Metropolitan Police spokesman also told The Express that the substance has not been identified.
The London Fire Brigade and London Ambulance Service attended the incident. There's no evidence that attack was gang related, officers say.
"Surrounding roads have been closed as an investigation is underway".
Police are still investigating into the cause of the chemical burns.
No arrests have yet been made, according to the Met.
Anyone with information that may assist police should call detectives from Hackney CID via 101.